1. Field of the Invention
The present invention relates to a novel cosmetic composition, and, more particularly, to a cosmetic composition comprising a long-chain alkyltrimethylol which exhibits superior extendibility when applied, imparts a non-sticky, fresh feeling upon use, and provides an excellent moisture-retaining effect. The cosmetic composition possesses a good emulsion stability.
2. Description of the Background
Conventionally, various types of moisturizing agents have been used for cosmetic compositions. Such moisturizing agents do not exhibit sufficient effects if the amount formulated is small. If, on the other hand, a large amount is formulated, cosmetics tend to impart an unfavorable feeling to the skin or their stability tends to be impaired.
Emulsion type cosmetics are widely used owing to their capability of imparting both oil and water to skins and hairs. Various types of emulsion type cosmetics with varied characteristics and sensation upon use can be prepared by changing the types and amounts of oil components.
An emulsion, however, is a thermodynamically unstable system. Various attempts and studies have been undertaken to stabilize emulsion systems. One of the measures of the emulsion system stabilization is the use of emulsifying adjuvants. Such emulsifying adjuvants include cationic-, anionic-, amphoteric-, and nonionic type. Of these, nonionic type is preferable because of its broader spectrum of oil components which can be used together.
Higher alcohols such as cetanol and cetostearyl alcohol are known as examples of nonionic type emulsifying adjuvant. Addition of such a higher alcohol to a cosmetic emulsion produces a liquid crystal structure and this structure helps the emulsion to stabilize. The addition of a higher alcohol is effective from the aspect of preventing oils and fats having a high melting point from crystallizing. However, if a higher alcohol is added in an amount sufficient to maintain such oils and fats in a stable condition, viscosity of the cosmetic becomes so high that it cannot adequately extend on the skin when applied and imparts an excessive oily, sticky sensation. In addition, the liquid crystal structure produced by the use of a higher alcohol, when destroyed, deposits crystals having pearl-like gloss and lowers the viscosity of the composition.
In order to overcome such defects in liquid crystal structures, compositions to which a nonionic type emulsifying adjuvant capable of producing a lamella type liquid crystal structure have been developed. For example, Japanese Patent Publication No. 5050/1963 discloses a skin and hair protecting agent comprising a triol represented by the formula (II): ##STR2## wherein n is an integer of 1-3.
The triol, however, has a defect of forming liquid crystals with a reversed middle structure in an aqueous solution which imparts an oily sensation and does not exhibit a sufficient moisture-retaining effect. Japanese Patent Laid-open No. 23737/1988 discloses an aqueous niosome dispersion comprising lipid lamella formed using polyglycerolether as a nonionic amphiphilic compound in an attempt to promote the stability by encapsulating water-soluble active components in an aqueous compartment which is encircled by lipid layers. Such an aqueous niosome dispersion, however, requires treatment at a high temperature of above 80.degree. C. to produce a niosome encapsulating active components. This makes it difficult to apply the method to active components which are not stable at a high temperature. Japanese Patent Publication No. 8287/1983, Japanese Patent Publication No. 56016/1986, Japanese Patent Laid-open No. 77613/1982, and Japanese Patent Laid-open No. 94326/1982 disclose aqueous dispersions of lipid spheres by the use of polyglycerolether. Industrial production of aqueous dispersions of lipid spheres, however, involves difficulties such as requirement of a homogenizing procedure, use of organic solvents such as chloroform and methanol for dissolving lipids, complicated vaporization processes for removing the solvents, etc.
Nonionic emulsifying adjuvants conventionally used thus have drawbacks in that they have narrow concentration ranges for liquid crystal formation, require a high temperature for forming liquid crystals, and are difficult to produce liquid crystals industrially.
Cosmetic compositions in which high melting point active components are not uniformly dispersed or adequately emulsified do not exhibit a sufficient moisture-retaining effect. Although some nonionic emulsifying adjuvants can exhibit moisturizing effects such effects are not sufficient.
Accordingly, development of cosmetic compositions which do not cause crystal transformation and remain homogeneous with superior stability over a wide range of temperature at which they are used, and which do not impart oily sensation and exhibit an excellent moisturizing effect has been desired.
In view of this situation, the present inventors have conducted extensive studies to resolve the above-mentioned problems in conventional cosmetic compositions, and found that cosmetic compositions having an excellent moisturizing effect could be produced by the use of a certain type of long-chain alkyltrimethylol and that if such a long-chain alkyltrimethylol is formulated in emulsion type cosmetic compositions, in addition to the excellent moisturizing effect, further effects could be obtained such as stabilizing emulsions and broadening the range in which high boiling point active components are maintained homogeneous. The inventors have further found that the emulsion cosmetic compositions exhibited superior extendibility when applied and imparted a non-sticky, fresh feeling upon use. Such findings have led to the completion of the present invention.